PCSK9 and obesity due to melanocortin 4 receptor deficiency: For example, physiologic dissection of the actions of soluble proteins such as proprotein convertase subtilisin/kexin type 9 (PCSK9) and glucagon-like peptide 1 (GLP1) have yielded among the most promising therapeutics to treat cardiovascular disease and obesity, respectively (Drucker, 2022; Trapp and Stanford, 2022; Dadu and Ballantyne, 2014; Lambert et al., 2012).